Originally Posted by
ssl92677
My understanding is the pump runs on startup for a short period for initial fuel/air mixture adjustment until CATS attain temperature and the ECU takes over. My experience was the P410 code was generated because although the pump ran correctly at startup, the dirty/corroded contacts on the RCM relay caused the relay to intermittently chatter (make/break) while driving. It took awhile but I finally made this observation when came to a stop at a light one day and I heared the high-pitched whine coming from the the air pump again uneccessarily. Fortunately, replacing the RCM solved the issue for me without needing to replace/rebuild the air pump.
Sometimes a relay sticks, especially when the contact points are badly pitted and an increase of current 'welds' the contacts together. This is intermittent at best since a vibration can 'break' that bad weld loose. Also, the pump on the N/A will also intermittently run after a cruise, when you decelerate and stop (like at a light). It is only the sensors reacting to the specific readings to inject fresher air into the exhaust. It is normal to have the pump run on occasion after the engine is warmed up. It runs based on the load and how the sensors read the exhaust.
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